3-(hydrocarbonthio)-2-(tri-o-benzoylribofuranosyl)-as-triazin-5(2h)-ones and process therefor



United States Patent 3 (HYDRSCAREQNTHZQ) 2 (FRI 0 BENZGYL-RESOFURANOSYL) as TREAZHQ 5(21-1) QNES AND PROCESE; THEREFGR Albert R.Restivo, Bellevilie, NJ., assignor to Olin Mathieson Chemical Company,New York, N.Y., a corporation of Virginia No Drawing. Filed June 30,1960, Ser. No. 39,768

4 Claims. (Cl. 260-2115) This invention relates to the synthesis ofheterocyclic organic compounds. More particularly, this inventionrelates to the synthesis of crystalline2-ribofuranosyl-as-triazin-3,5(2H,4H)-dione (i.e., azauridine) by a newand improved method.

Azauridine is a known compound. The first reported chemical synthesis ofit involved the reaction mercuric chloride with azauricil, treatrnent ofthe mercurated product with 1-O-acetyl-2,3,5-tribenzoyl-d-ri'oofuranose,and debenzoylation of the resulting ribofuranosyl derivative to yieldthe desired compound. This process while yielding wherein R is ahydrocarbon radical of less than twelve carbon atoms such as: alkyl,especially lower alkyl (e.g., methyl, ethyl, propyl, butyl, amyl andhexyl), aralkyl, especially monocyclic aryl lower alkyl (e.g., benzyl,phenethyl, ,B-phenylpropyl, and o,m or p-tolylethyl), alkenyl especiallylower alkenyl (e.g., allyl), aralkenyl especially monocyclic aryl loweralhenyl (e.g., cinnamyl) and cycloalkyl (e.g., cyclopropyl andcyclohexyl), with a mercuric salt. Preferably, the acid moiety is thator" an acid, such as the hydrohalic acids (e.g., hydrochloric andhydrobromic acids), nitric acid, sulfuric acid and organic acids, suchas the lower alkanoic acids (e.g., acetic, propionic and butyric acids)and aromatic acids (e.g., benzoic and o,m and p-toluic acids) to form acompound of the Formula II:

wherein R is as above defined, X is the anion of the divalent mercuricacid salt and n is the integer one or two.

The reaction is preferably conducted in an inert solvent medium, such asthe lower alkanols' (e.g., methanol and ethanol) and dimethylformamide.Reaction speed may be increased by warming the solution of the tworeactants, but reaction will occur at room temperature. The ratio ofreactants will determine the nature of the reaction product to theextent that if two moles of the triazine are employed for each mole ofhe mercuric salt, the reaction product will contain two moles of thetriazinyl moiety whereas if a one to one ratio is employed, the reaction3,135,737 Patented June 2, 1964 product will be a mercuric acid salt ofFormula II wherein n is equal to one.

A compound of Formula II is next reacted with tri-O-benzoyl-D-ribofuranosyl chloride to yield a compound of the Formula III:

N (trl-o-benzoylnbofuranosyl) -N wherein R is as hereinbefore defined.The reaction is conducted in a solvent medium and preferably underreflux conditions. Suitable solvents are non-polar solvents such as thearomatic hydrocarbons (e.g., benzene and toluene). The reaction productis isolated from the liquid portion of the reaction mixture byfiltration and concentration of the filtrate.

Compounds of Formula III are converted to the compound 2(tri-O-benzoylribofnranosyl)-as-triazin-3,5(2ll, 4H)-dione byhydrolytically removing the 3-RS-radical from the thiazinyl nucleus.This can readily be accomplished by treating the compounds of FormulaIII with an acidic aqueous alkanolic solution (e.g., hydrochloric acidin aqueous ethanol) under reflux conditions. The hydrolysis product isconverted to azauridine by further hydrolysis with a strong base such asaqueous ammonia.

The starting materials for this invention, i.e., the compounds ofFormula I, are new compounds prepared by first condensing substantiallyequimolar amounts of a solution glyoxylic acid (preferably as thehernihydrate) and thiosemicarbazide, in a suitable solvent such as alower allranol (e.g., methanol, ethanol or propanol). The condensationproduct is then treated in situ with a compound of the formula:R-l-lalide, wherein R is as hereinbefore def'med, the halide preferablybeing iodide. The alkyiation is conducted under basic conditions (e.g.,in the presence of an alkali metal hydroxide such as sodiurn orpotassium hydroxide). The compound of Formula I is separated from thereaction mixture by filtration. It may be used in this form or furtherpurified as desired, in carrying the process of this invention.

Alternatively, the compounds of Formula I may be prepared by thecondensation reaction of glyoxylic acid (preferably as the hemihydrate)with a salt (preferably a h drohalide) of 3-R-thiosemicarbazide, whereinR is as hereinbefore defined, in the presence of a strong base such asan alkali metal hydroxide (e.g., sodium or potassium hydroxide). Theproduct may be separated from the reaction mixture by the separationprocedure hereinbefore noted, or it may be employed in the nextsynthetic step without further purification.

The following examples are presented to more fully illustrate theinvention, all temperatures-being expressed in degrees Centigrade.

EXAMPLE 1 3- (M ethylthio) ,2,4-as-Triazin-5- (2H -One To a solution of82.3 g. (0.9 moles) of thiosemicarbazide in 2.25 Lot ethanol at 70 isadded 89.9 g. (0.9 moles) of glyoxylic acid, hemihydrate in 450 ml. of80% ethanol. After a few minutes the solution is diluted with 250 ml. Nsodium hydroxide (1.0 moles) followed by addition of 142 g. (1.0 moles)of methyl iodide. The mixture is refluxed for 2% hours and thenconcentrated to one-third the original volume. After cooling the crudeproduct is filtered and recrystallized from ethyl acetate to yield about65.0 g. of 3-(methylthio)-1,2,4-as-triazin-5-(2H)-one, M.P. 221-222".

Analysis.-Calcd for C H N OS: N, 29.35; S, 22.40.

' Found: N, 29.03; S, 22.56.

' tri-O-benzoyl-D-ribofuranosyl chloride in benzene.

EXAMPLE 2 3-(Benzyllhz'0) -1,2,4-qs-Triazine-5- (2H) -One EXAMPLE 3 (Metlzylthio) ,2,4-as-T riazine-5 (2H -One A suspension of 45.6 g. (0.5moles) of thiosemicarbazide in 900 ml. of absolute ethanol is heated to40.

' After adding 71.0 g. (0.5 moles) of methyl iodide the resultingsolution is refluxed for 1% hours. On cooling the white precipitate isfiltered and washed with ether to give about 68.8 g.:of3-methylthiosemicarbazide, M.P. 136-137". A second crop of 8. 4 g. ofproduct, M.P. 136137 is obtained fromthe mother liquor.

A solution of 17.2 g. of the 3-methylthiosemicarbazide in 90 ml. of H istreated at room temperature with a solution of 5.8 g. of glyoxylic acidhemihydrate in 75 ml. of N NaOl-I. After cooling, the precipitate(presumably 3-methylthiosemicarbazone, glyoxylic acid) is filtered togive 11.16 g. of material M.P. 180190. When this material is refluxed in700 ml. of 95% ethanol for 3 hours there is separated a total of 2.67 g.of B-methylthio-1,2,4-as-triazin-5-(2H)-one.

. EMMPLE 4 2,2'-M ei'curibis- [3- (M ethylthz'0)-as-T riazin-S- (211)-One] 7 A warm solution of 6.38 g. (0.02 moles) of mercuric acetate in50 ml. of methanol is added to a Warm solution of 5.72 g. (0.04 moles)of the product of Example 1. After cooling, the precipitate is filteredand washed successively with water, ethanol and ether giving about 8.6g. of 2,2-mercuribis-[3-(methylthio)-as-triazin- S-(ZH) one] having thefollowing analysis.

Analysis.Calcfd for C l-l N S O Hg: N, 17.33. Found: N, 16.77.

- EXAMPLE 5 2- Ch loromercuri -3- (M ethylthio) -as-T rz'azin-S(2H)r0l18 EXAMPLE 6 2,2'-Mercuribis-[3-(Benzylthi0)-as-Triazin-5-(2H)-One] Following the procedure of Example 4 except for thesubstitution of 8.76 g. of the product of Example 2 as the startingmaterial, there is obtained the product 2,2- mercuribis- [3- (benzylthio-as-triazin-5- (2H) -one] EXAMPLE '7 3- (Methylthio)-2-(Tri-O-Benzoylribofuranosyl)- as-Triazir -5-(2H)-0ne EXAMPLE 8 3-(Benzy lthz'o) -2- Tri-O-Benzoylribofuranosyl as-Triazin-5- (2H) -OneFollowing the procedure of Example 7 except for the substitution of 4.93g. of the product of Example 6 as starting material, there isobtained asfinal productthe compound 3 (benzylthio) 2-trio-O-benzoylribofuranosyl)-as-triazin-5 (2H) -one.

EXAMPLE 9 3 (M ethylthio) -2- Tri-O-Benzoylribofuranosyl as-Trz'aziu-5-(2H) -One To a suspension of 5.86 g. of the product of Example 5 in 100ml. of toluene is added 15.0 g. of tri-O-benzoyl- D-riboiuranosylchloride in benzene. The mixture is distilled to remove the benzene andthen refluxed for 34 hours, cooled and filtered. The filtrate isconcentrated to dryness and the residue picked up in chloroform. Theextract is Washed with dilute KI solution,

' water, dried and then concentrated to leave as residue the product 3(methylthio)-2-(tri-O-benzoylribofuranosyl)a as-triazin-5-(2H)one.

EXAMPLE 10 A. From 3-(methylthio) 2(tri-O-benzoylribofuranosyl)-as-triazin-5-(2l-l)-one 0.59 g. of theproduct of Example 7 is dissolved in 200 ml. of 95% ethanol, and thesolution is treated with concentrated HCl and refluxed for 1% hours.slightly, whereupon crystals form. The crystals are filtered ott andthen recrystallized from ethyl acetate yield ing substantially pure 2(tri-O-benzoylribofuranosyl)- v as-triazin-3,5-(2H,4H)-dione having thefollowing characteristics: M.P. about 191-194.

Analysis.-Calcd for C29H23N309: C, H, N, 7.55. Found: C, 62.02; H, 4.11;N, 7.53.

B. From 3(benzylthio)-2-(tri-O-benzoylribofuranosyl)-as-triazin-5-(2H)-one anequivalent amount of the product of Example 8 is substituted as startingmaterial in the procedure of part A supra to yield a product To a drysuspension of 3.76 g. of the product of which is the same as the productobtained in part A.

EXAMPLE 11 157159 (undepressed on admixture with authentic material,produced biosynthetically); with U.V.

and infra red determinations also being identical with authenticmaterial.

Analysis.-Calcd for C l-1 N 0 C, 39.19; H, 4.52; N, 17.14. Found: C,39.79; H, 4.56; N, 17.34.

This invention may be variously otherwise embodied The solution is thenconcentrated The wherein R is a hydrocarbon radical of less than twelvecarbon atoms.

2. The compound 3-(methylthio) -2-(tri-O-benzoylribo furanosyl)-as-triazin-5 (2H)-one.

3. The compound 3-(benzylthio)-2-(tri-O-benzoy1ribo furanosyl)-as-triazin-5 (2H)-one.

4. A process for the preparation of a compound of claim 1 whichcomprises reacting a compound of the formula wherein R is a hydrocarbonradical of less than twelve carbon atoms; X is an anion of a divalentmercuric acid :5 salt; and n is an integer selected from the groupconsisting of 1 and 2, with tri-G-benzoyl-ribofuranosyl chloride.

References Cited in the file of this patent UNITED STATES PATENTS2,792,392 Freedman May 14, 1957 2,792,393 Shapiro May 14, 1957 2,852,505Baker Sept. 16, 1958 2,885,396 Heidelberger et a1 May 5, 1959 2,935,508Shunk May 3, 1960 OTHER REFERENCES Cattelain et al., Academic desSciences Comptes Rendns, tome 218, pages 623624 (Ian-lune 1944).

Gut, Collection of Czechoslovak Chemical Communications, vol. 23, pages1588-1591 (May-Aug. 1958).

1. A COMPOUND OF THE FORMULA: